Adam Lanza quarreled with four teachers day before he shot three

Reports say that Adam Lanza visited the school the day before the massacre and was involved in an altercation with four members of the school staff. He killed three of the staff members the next day, the fourth escaped because she was not at school.

According to the Daily Mail, Lanza reportedly got into an altercation with members of staff, including Principal Dawn Hochsprung and teacher Victoria Soto both of whom he shot the next day.

Reuters reports that the issue involved his mother with whom he got so enraged that he shot her in the face and then drove, presumably in rage, to Sandy Hook Elementary School, armed with three guns he drew from his mother's arsenal and shot three other teachers he had quarreled with the day before.

The fourth teacher who escaped being shot because she was not at school is now being interviewed by police investigators who have not revealed the subject of the argument between the teachers and Lanza.

Police are hoping that the testimony of the survivor would help to establish the motive behind the shooting. The Daily Mail reports that Connecticut State Police Lieutenant Paul Vance, said: "Our investigators at the crime scene ... did produce some very good evidence in this investigation that our investigators will be able to use in, hopefully, painting the complete picture as to how - and more importantly why - this occurred. We're hopeful it will paint a complete picture."

According to the police, Adam Lanza, contrary to reports that the school principal Mrs Hochsprung, allowed him to by-pass the newly-installed security system, forced his way in. Reuters reports that the school had installed a buzzer on the front door and a security camera in the hall shortly before the shooting.

The Hartford Courant reports that a letter the school principal sent to parents after the security system was installed, said:

Dear Members of our Sandy Hook Family,

Our district will be implementing a security system in all elementary schools as part of our ongoing efforts to ensure student safety. As usual, exterior doors will be locked during the day. Every visitor will be required to ring the doorbell at the front entrance and the office staff will use a visual monitoring system to allow entry. Visitors will still be required to report directly to the office and sign in. If our office staff does not recognize you, you will be required to show identification with a picture id. Please understand that with nearly 700 students and over 1,000 parents representing 500 SHS families, most parents will be asked to show identification.

Digital Journal reports that after he forced his way into the school building on Friday morning, Lanza opened fire, murdering 26 people before turning the gun on himself. The Daily Mail reports that the tragedy struck as the school opened for first lessons in the morning.

According to Digital Journal, he massacred nearly an entire classroom of students before he moved to the next where he shot several. The Daily Mail reports witnesses say he may have fired as many as a 100 rounds.

According to Digital Journal, his former high school mates remember him as an awkward "nerd" who kept to himself, though he was academically brighter than most.

Digital Journal reports that his mother was an avid gun collector who legally owned a Sig Sauer and a Glock. The Daily Mail reports that both handguns he reportedly used in the shooting belonged to his mother and were models commonly used by police. He also carried a military-style Bushmaster .223 M4 carbine that belonged to his mother.

The Daily Mail reports that Dan Holmes, owner of a landscaping business who helped to decorate Nancy Lanza's yard with Christmas garlands and lights, said she once showed him a "really nice, high-end rifle" she had purchased. She told him "she would often go target shooting with her kids."

The death toll from the shooting exceeded the notorious 1999 shooting involving two teenagers at Columbine High School in Littleton, Colorado, who murdered 13 students and staff before killing themselves, the Daily Mail reports.